1. Field of the Invention
The present invention relates to a counting circuit arrangement for a coin counting device, and particularly to a circuit arrangement provided with an alarm generating section for generating an alarm signal when dust or other foreign matter adheres to the optical counting elements of the system for counting coins.
2. Prior Art
Optical counting systems for counting passing coins have been known in the art. An illustrative example of the known optical counting systems is shown in FIG. 1. Referring to FIG. 1 showing main parts of the illustrative example, the structure and operation of the known system will be outline.
In FIG. 1, coins are charged on a rotary disk 1 rotating in the direction shown by the arrow A, and then introduced to a coin passage 2 successively one by one. The coins are passed through the coin passage 2 under the action of a guide belt 3 to a coin accumulator tube 4 in which they are accumulated. Along the coin passage 2, there are provided a stopper pin 5 to open or close the coin passage 2 and two photosensors 6 and 7 for detecting the coins passing through the coin passage 2. A light emitting element (not shown) is disposed above the photosensors 6 and 7 in opposed relationship to the photosensors, and the passing coins interrupt the light paths from the light emitting element to the photosensors 6 and 7.
The photosensors 6 and 7 detect the traveling direction of the passing coins and simultaneously count the number of the coins passing therethrough. The counted coins are introduced into the coin accumulator tube 4. When the number of coins accumulated in the accumulator tube reaches the pre-set number, the stopper pin 5 is rotated by 90.degree. by rotary solenoid (not shown) in the direction shown by the arrow B to stop the feeding of coins to the accumulator tube 4.
However, in the prior art device, if dust or other foreign matter should adhere to either one of the photosensors 6 or 7, the moving direction of the coins cannot be detected and only the passage of coins can be detected, resulting in miscounting. There is another problem that a signal causing the miscounting in the counting circuit might be generated when dust or other foreign matter adheres to either one of the optical elements or due to reduction in illuminating power of the light emitting element to lessen the quantiy of light incident onto the photosensors 6 and 7.